Why does rref() make a sound sample sound different?

Question

Mara Gati 2016-5-3

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评论： Mara Gati 2016-5-6

I was messing around the other day and ended up with the following code:

load handel
h = [y;Fs];
h = h';
d = rref(h);
sound(d)

What does rref() do to make it sound like that?

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Answer 1

Star Strider 2016-5-3

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It depends on how you give rref the matrix. (Stereo sound files are (Nx2) matrices.)

If you give it as the two-column matrix, you get the result that John describes. If you transpose the matrix (to (2xN), you get an entirely different result.

Experiment:

t = linspace(0, 2)';
M = [sin(2*pi*t)  cos(2*pi*t)];                     % Create Data
figure(1)
subplot(2,1,1)
plot(t, M)
hold on
plot(t, rref(M), '--')
hold off
grid
subplot(2,1,2)
plot(t, M)
hold on
plot(t, rref(M'), '--')
hold off
grid

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Answer 2

John D'Errico 2016-5-3

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Why in the name of god and little green apples would you bother to do this? rref is a linear algebra tool, normally applied to matrices, for a specific purpose. Throwing random numbers into a random function will yield randomly meaningless (and useless) results.

d is a column vector as you create it. rref will take ANY column vector with at least one non-zero element, and return a vector which is entirely zero, except that the first element is 1.

When you then put that into the sound function, it sounds as it does.